This invention relates to pneumatic tires and rim. More specifically, the invention relates to a modified rim for automobiles and light trucks. The rim having a 5xc2x0 drop center profile and a unique flange.
Over the years, the tubeless pneumatic tire and its associated rim have been designed to make an efficient wheel assembly. The rim provides a means to attach the wheel to the vehicle; it provides a space to locate and attach the brake assembly and finally and foremost, it provides a bead seat and rim flange designed to accept a tire and to secure that tire creating an air-tight seal between the rim and the tire.
The combination of the tire and the rim flange also provides a surface to attach leaded balancing weights to reduce rim and tire vibration due to out of balance conditions.
The rim is a most efficient mechanical structure performing all of the functions described above in one well engineered structure.
The rim has evolved over the years from a cold, rolled steel structure to highly engineered cast magnesium or aluminum structure of very light weight.
The tire engineer has rarely been a significant contributor to the evolution of the rim. Radical and usually complex rims have been suggested by various tire companies to solve a difficult problem in the tire.
Almost universally, these rim solutions meet with failure and very poor market acceptance.
The early evolution of so-called safety tires and runflat tires all have suggested designing a special rim and tire combination. Experience dictates that the tire engineer preferably should solve his or her tire related problems within the standards already established in the United States, Europe and Japan.
Nevertheless, slight deviations from the proven standards has led to some remarkable benefits.
Jacques Boileau of Michelin disclosed in U.S. Pat. No. 3,910,336 that low aspect ratio radial tires could be designed and molded wherein the carcass reinforcement could follow a neutral ply line if the standard rim flange did not interfere. He suggested that the conical edges of the rim should be located above the bead core, however, the edge in accordance to the invention is generally less high seen in the radial section than a conventional rim. Boileau further teaches that, for these rim edge flanges to achieve the desired contoured, they should be inclined between 20xc2x0 and 60xc2x0 preferably close to 45xc2x0 to give the desired results.
Boileau""s rim in combination with a tire molded with a specified cord ply path that was neutral yields improved ride and comfort.
Nevertheless, the radially outer portion of the rim flange was designed to be above the tire bead core and in contact with the bead portion of the tire. This was necessarily, or at least considered necessary in part, due to the use of a light weight round cable bead core which increased the flexibility of the tire in the bead region.
In European Patent Application 0 278 615, assigned to S P Tyres UK Limited, a conventional rim flange was modified by providing one retaining flange of reduced height along a portion of the flange extending a length of 0.25 to 0.5 times the bead seat circumference. The assembly provided a wheel rim having much increased break space inside the wheel rim.
The present invention utilized a unique rim that has no portion of rim extending above the radially outermost portion of the bead core of the tire.
It is an object of the present invention to provide a 5xc2x0 bead seat rim with a reduced radial height rim flange that will not contact the tire at any location above the bead core during any driving conditions.
It is a further objective that the rim flange securely restrains the beads laterally without contributing any radial input to the tire.
It is a further object of the invention to provide a modified rim for low aspect ratio tires of 65% or less of any ply path wherein the rim flange cannot adversely input the ride and handling performance of the tire.
A tire rim (1, 40, 60) has an axially inboard and an axially outboard end, a pair of annular flanges (2, 42, 62) at both axial ends, respectively a pair of bead seats (3) axially inwardly extending from the flanges (2, 42, 62). The rim (1, 40, 60) has a reduced diameter central portion (4) between the opposing bead seats (3). A bead hump (5, 6) is adjacent each bead seat (3). One inclined surface (8) extends between the reduced diameter central portion (4) and the bead hump (5, 6) nearest the annular flange (2, 42, 62) located adjacent the axially outboard side.
The tire rim is (1, 40, 60) characterized by each annular flange (2, 42, 62) having a maximum radial height (h) less than 12 mm, preferably in the range of 6 mm to less than 12 m, most preferably about 9 mm.
In one embodiment the annular flanges (2) have an almost vertical axially innermost surface (32) extending generally from above the bead seat (3) to just below the radially outermost portion (30) of the respective rim (1) flange (2) defining the maximum radial height (h).
In an alternative embodiment (40), the axially innermost surface (52) of the rim flange (42) is inclined axially and radially outwardly at an angle greater than 60xc2x0 relative to the rim""s axis.
The rim (1, 40, 60), when used in combination with a tire (10), forms a tire and rim assembly wherein the tire (10) has tread portion (12), a tread reinforcement (14) in the tread portion (12), a pair of sidewalls (16) respectively on opposite sides of the tread portion (12), a pair of beads (20) respective at the radially inner edges of the sidewalls (16), a bead core (22) respectively in each of the beads (20) and a carcass reinforcement (18) having cords (19) that are radially extending, the tire (10) having an aspect ratio of less than 65%.
The rim (1, 40, 60) correspondingly has an axially inboard and an axially outboard end, a pair of annular flanges (2, 42, 62) at both axial ends, respectively a pair of bead seats (3) axially inwardly extending from the flanges (2, 42, 62). The rim (1, 40, 60) has a reduced diameter central portion (4) between the opposing bead seats (3). A bead hump (5, 6) is adjacent each bead seat (3). One inclined surface (8) extends between the reduced diameter central portion (4) and the bead hump (5, 6) nearest the annular flange (2, 42, 62) located adjacent the axially outboard side.
The tire (10) and rim (1, 40, 60) assembly is characterized in that each annular flange (2, 42, 62) of the rim (1, 40, 60) has a maximum radial height (h), (h) being less than 12 mm and each bead core (22) has a cross-sectional area having a centroid (24) located radially less than 12 mm from the bead seat (3), preferably the centroid (24) is located 9 mm or less from the bead seat (3). The maximum radial height (h) of the flange (2, 42, 62) is preferably within 3 mm of the radial location of the bead core (22), most preferably within 1 mm.